Hydrogen Production from Low-Grade Water Electrolysis to Contribute to Sustainable Development Goals 6 and 7: Challenges and Opportunities

Abstract

The nexus between water and energy plays a key role in the green hydrogen economy. Conventional water electrolyzers require high purity water. This can create a burden on the freshwater facilities, in water stressed regions, for the mass production of green hydrogen. In this context, this paper explores the potential of nonpotable water sources, such as untreated sea and brackish water and waste water, as feedstock for water electrolyzers to produce green hydrogen, thereby contributing to United Nation’s sustainable development goals 6 and 7. We discuss the ionic impurities composition, variability of these low-grade water types and electrochemical challenges arising from these impurities. This includes undesired reactions, scaling, and degradation of catalyst and membrane degradation. We highlight the strategies to overcome these challenges, i.e., selection of novel electrocatalysts for impure water electrolysis and design of electrolyzers such as membraneless flow water electrolyzer that leverages hydrodynamic flow to separate the produced hydrogen and oxygen gasses without the costly and impurity sensitive membranes understood from computational fluid dynamics simulation results. We further propose the concept of integration of these membraneless flow electrolyzers with wastewater pipelines to support the decentralized hydrogen production. The techno-economic analysis further supports the integration of low-grade water with the proposed membraneless water electrolyzers. These advances can pave the pathway toward resource efficient and decentralized hydrogen production that aligns with global sustainability and clean energy goals.